In an unusually late 1 AM reveal for Japan, Magcargo-GX has just been revealed from SM7a Thunderclap Spark! The set will release in Japan on July 6th. Thanks goes to Bangiras for the translation!
Ability: Crush Charge
Once during your turn (before your attack), you may discard the top card from your deck. If that card is a basic Energy card, attach it to 1 of your Pokemon.
[R][R][C] Lava Flow: 50+ damage. You may discard any number of basic Energy cards from this Pokemon. This attack does 50 more damage for each card discarded in this way.
[R] Magma Burn GX: Discard the top 5 cards from your opponent’s deck. (You can’t use more than 1 GX attack in a game.)
When 1 of your Pokemon-GX is Knocked Out, your opponent takes 2 Prize cards.
Weakness: Water (x2)